First spectrum and interpretation of the results

[Falcon]

So I've been working with my GS-USB-pro for a little while now, mostly using known single element sources.

This time I've have analysed a truly unknown sample and I'm working on interpreting the results.
Conditions;
PRA v20: total time 3600 sec for total count of 390,000 pulses
Sample: roughly 5g of white powder contained in glass vial (this sample was a residue produced during the extraction of uranium from ore, so I would expect it to contain an isotope of the 238 decay series).
Shield: 20mm thick lead, 3mm thick tin, 1.0mm thick copper - for average background of 4 cps
Calibration: Lu metal (1g) using 202 and 307 keV, and 1460 keV KCl

Results:

Bi Pb Po oxide 3600s 190209.jpg

Energy/(keV)
Start End Mean SD Gross Net
51.439 59.155 55.453 1.598 14361 551
72.014 118.309 92.994 10.132 129385 65737
138.885 169.748 154.964 7.433 38868 8173
219.495 293.19 257.986 15.794 63272 20372
337.017 377.4 359.391 7.211 14063 1155
413.295 449.19 432.951 5.208 5295 359
660.075 700.457 683.107 6.226 1421 189
888.907 951.723 918.534 11.045 1247 152

So the main point I can tell is the peak(s) at 93keV which is likely Th234. As for the others I haven't had much luck (could be the way I'm determining mean peak position?)
I'm using the gamma energy tables from the CRC handbook 62nd edition for interpretation of the results.

So my question is how do you go about interpreting the results? As there are backscatter, xrays and gamma peaks that all makeup the spectrum, is there a way to understand these results without having to know every possible peak?

[Sesselmann]

Hi Lachlan,

Thanks for posting.

Your spectrum looks nice and sharp, with clearly defined peaks. The fat fourth peak looks like it could be two peaks close to each other.

You might see more detail at the top end if you view the spectrum in log scale.

My approach would be to go for the known peaks and do a multi point calibration with those (assuming there are some obvious ones).

Then you can find the link to the Lund/LBNL database here https://www.gammaspectacular.com/blue/links

You can search the database either by energy or isotope and it will list all the known gamma rays and x-rays.

Good luck and please post your findings.

Steven